CYCLOPÆDIA, or ENCYCLOPÆDIA, in modern usage a work professing to give information in regard to the whole circle of human knowledge, or in regard to everything included within some particular scientific or conventional division of it. The character of such works has of necessity varied from generation to generation, with changing conceptions of the scope and value of our knowledge and of the mutual relations of one department with another.

Though several of the ancient philosophers of Greece, and notably Aristotle, carried their investigations into every department of inquiry within their intellectual horizon, none of them seems to have compiled exactly what we now call a cyclopædia. Speusippus, indeed, is credited with something of the sort; but his works exist only in fragments. The great Latin collections of Terentius Varro, dating from 30 B. C., and the so-called “Historia Naturalis” of the elder Pliny (23-79 A. D.), may thus be considered as the first specimens of their class. The 5th century saw the production of a curious and oddly written cyclopædia by Martianus Capella; in the 7th, Isidorus Hispalensis compiled his “Originum seu Etymologiarum libri xx,” which was afterward abridged and recast by Hrabanus Maurus. Under the caliph of Bagdad, Alfarabius or Farabi, in the 10th century, wrote a cyclopaedic work, “Ihsa Alulum” — remarkable for its grasp and completeness; but this has hitherto been left in manuscript (a fine copy is preserved in the Escurial). Vincent of Beauvais (Vincentius Bellovacensis), who probably died in 1264, gathered together, under the patronage of Louis IX. of France, the entire knowledge of the Middle Ages in three comprehensive works — “Speculum Historiale,” “Speculum Naturale,” and “Speculum Doctrinale,” to which an unknown hand soon after added a “Speculum Morale.” About the same time Brunetto Latini was engaged on his “Livres dou Tresor” (printed in Italian in 1474, and in the original French in “Documents inédits” (1680). The “De proprietatibus rerum” of Bartholomeus de Glanville deserves mention as being of English origin and highly successful in its day.

Written about 1360, this became exceedingly popular in the translation (1398) by John Trevisa. In 1541 the name cyclopædia is first used as the title of a book by Ringelberg of Basel, and in 1559 Paul Scalich styles his work “Encyclopædia seu orbis Disciplinarum tum Sacrarum tum Profanarium.” Among the numerous cyclopædias of the 17th century it is enough to mention Antonio Zara's (Venice, 1615), and Alsted's (7 vols, fol. Herborn, 1630), both in Latin; Moreri's “Grand Dictionnaire Historique” (Lyons, 1674), which reached a 20th edition in 1759; Hofmann's “Lexicon Universale” (2 vols., fol. Basel, 1677; 4 vols. fol. Leyd. 1698), which was the first attempt to bring the whole body of science and art under the lexicographic form; Thomas Corneille's “Dictionnaire des Arts et des Sciences” (2 vols. Paris, 1694); and the most famous of all, Bayle's “Dictionnaire Historique et Critique” (4 vols. Rotterdam 1697), which was mainly designed as corrective and supplementary to Moreri.

It was in the course of the 17th century that the cyclopedists began regularly to employ the vulgar tongues for their work, and to arrange their material alphabetically for convenience of consultation. Of the vast “Bibliotheca Universale,” planned by Coronelli to fill 45 folio volumes, only a small portion saw the light (Venice, 1701-1706). The series of great cycolpædic works in modern English practically began by the anonymous “Universal, Historical, Geographical, Chronological, and Classical Dictionary” (2 vols. 1703), and the “Lexicon Technicum” of Dr. John Harris (Lond. 1704). Ephraim Chambers followed in 1728 with his “Cyclopædia, or an Universal Dictionary of Arts and Sciences” (2 vols, fol.), which presents a distinct advance in the construction of such works, the author endeavoring to give to his alphabetically arranged materials something of the interest of a continuous discourse by a system of cross references.

It was a French translation by John Mills of Chambers' “Cyclopædia” which originally formed the basis of that famous “Encyclopédie” which, becoming in the hands of D'Alembert and Diderot the organ of the most advanced and revolutionary opinions of the time, was the object of the most violent persecution by the conservative party in Church and State, and suffered egregious mutilations at the hands not only of hostile censors but of timorous printers. Appearing at Paris in 28 vols, between 1751 and 1772, it was followed by a supplement in 5 vols. (Amst. 1776-1777), and an analytical index in 2 vols. (Paris, 1780). Voltaire's “Questions sur l'Encyclopédie” (1770) was a kind of critical appendix. La Porte's “Esprit de l'Encyclopédie” (Paris, 1768), gave a résumé of the more important articles, and under the same title Hennequin compiled a similar epitome (Paris, 1822-1823). Numerous editions of the whole work, more or less expurgated or recast, were issued outside of France; and many minor encyclopædias, such as Macquer's “Dictionnaire Portatif des Arts et Métiers” (1766), Barrow's “New and Universal Dictionary of Arts and Sciences” (1 vol. fol. 1753), and Croker, Williams, and Clerk's “Complete Dictionary of Arts and Sciences” (3 vols. fol. 1766), were to a considerable extent quarried out of their massive predecessor, or molded according to the method expounded by D'Alembert in his preliminary dissertation.

Between 1768 and 1771 there appeared at Edinburgh in 3 vols. 4to the first edition of the “Encyclopædia Britannica,” which was from the beginning a kind of compromise between the alphabetical and the scientific distribution of subjects. Colin Macfarquhar, Andrew Bell, and William Smellie share the credit of the plan. Biographical and historical articles were first introduced in the 2d edition (10 vols. 4to 1776-1784). It was revised in 1907.

During the period that the “Encyclopædia Britannica” has been growing from edition to edition, numerous important encyclopædias have appeared in English — the “Edinburgh Encyclopædia” (18 vols. 1810-1830), edited by Sir David Brewster; Wilkes's "Encyclopædia Londinensis (24 vols. 4to. Lond. 1810-1829); “Encyclopædia Perthensis” (23 vols. Edin. 1816), a striking proof of the energy of its compilers, Aitchison of Edinburgh and Morison of Perth; the “Encyclopædia Metropolitana” (30 vols. 1818-1845), arranged, according to a philosophic plan by Coleridge, in four divisions: (1) pure sciences, (2) mixed and applied sciences, (3) biography and history, and (4) miscellaneous and lexicographic articles; the “Penny Cyclopædia” edited by Charles Knight for the Society for the Diffusion of Useful Knowledge (29 vols., 2 supplemental, 1833-1846); and the “English Cyclopædia” (22 vols. 1853-1861; a synoptical index, 1862; four supp. vols. 1869-1873), founded on the copyright of the “Penny Cyclopædia,” but rearranged in four divisions — viz, geography, natural history, biography, and arts and sciences.

The cyclopædia now known as Brockhaus' “Conversations-Lexicon,” which was started by Löbel at Leipsic, in 1796, and passed into the hands of F. A. Brockhaus in 1808, gave a great impetus to the production of similar works. It is still one of the most popular of German encyclopædias. Its principal rivals are Pierer's, and Meyer's “Konversations-Lexikon.” The former (Altenburg, 1822-1836, 26 vols, with 14 supplemental vols. 1840-1856), which had somewhat fallen out of date, reappeared in 12 vols, in 1888-1893; while the latter has become in completeness and compression the best work of its kind (1st ed. 15 vols. Leop. 1857-1860), a striking characteristic being the free use made of maps, tabular conspectuses, woodcuts, and lithographic illustrations. The Brockhaus “Lexikon” became the basis, more or less entirely, of cyclopædias in most of the civilized languages of Europe — “Encyclopædia Española” (Madrid, 1848-1851); “Nuova Enciclopedia Popolare Italiana” (Turin, 1841-1851); “Nordisk Conversations-Lexikon” (5 vols. Copenhagen, 1858-1863; 3d edition, 1883, etc.). Four English works were professedly founded on it — “Encyclopædia Americana” (14 vols. Phila. 1829-1846); “New American Cyclopædia” (16 vols. New York, 1858-1864), edited by Ripley and Dana, and frequently quoted as “Appleton's” from the name of the publisher; the “Popular Cyclopædia” (7 vols. Glasgow, new ed., 1883); and “Chambers' Encyclopædia” (10 vols. Edin., 1860-1868, edited by Dr. Andrew Findlater; new ed. 10 vols., edited by David Patrick, 1888-1892).

An attempt to remedy the defect of protracted production has frequently led to the issue of supplemental volumes, planned so as to bring up the earlier articles to the same level as the later articles, in more than one instance, notably that of Brockhaus' and Meyer's “Konversations-Lexikon” and the New International Year Book.

In contrast with the larger cyclopædias may be mentioned the modern attempts to boil down the circles of the sciences into portable form. Thus Brockhaus issued a “Kleineres Conversations-Lexikon” (3 vols. Leip., 1854-1856; 4th ed. 2 vols. Leip., 1885); Meyer's “Konversations-Lexikon” is admirably epitomized in Meyer's “Handlexikon” (5th ed. 3 vols. Leip., 1892-1893); and Spemann issues a pocket encyclopædia (Küschner's) which is a model of compression. Similar English productions are Beeton's “Encyclopædia” (2 vols. 8vo, Lond., n. d.); Beeton's “Dictionary of Science” (8vo, Lond., n. d.), Champlin's “Young Folks' Cyclopædia of Common Things” (New York, 1879), with the English reissue known as Cox's “Little Encyclopædia of Common Things” (8vo, Lond., 1882; 3d ed. 1884); Champlin's “Young Folks' Cyclopædia of Persons and Places” (1880); “Hazell's Annual” is a yearly cyclopædic record; Sampson Low's “Pocket Cyclopædia” (1889); Phillip's “Million of Facts” (8vo, 1836; and later without date); and in more recent years many others.

Special Cyclopædias. — This class has naturally become more and more numerous; though in many cases the works are neither designated cyclopædia nor dictionary. A valuable series is Meyer's “Fach-Lexika” (general history, ancient history, philosophy, geography, etc.), which applies the method of the “dictionary” to the treatment of individual subjects in separate volumes, thus differing from Lardner's “Cabinet Cyclopædia,” and the “Encyclopædia Metropolitana,” which were practically a series of treatises.